1. Field of the Invention
The present invention relates to a technique for facilitating rewriting of data in a flash memory or other electrically rewritable external nonvolatile memory which is connected with a microcontroller.
2. Description of the Related Art
Data in an external nonvolatile memory such as a flash memory mounted on a system board is rewritten by detaching the external nonvolatile memory from the system board and attaching the detached external nonvolatile memory to a dedicated rewriting apparatus such as a flash writer. The external nonvolatile memory is mounted on the system board via an IC socket so that it can be detached from the system board easily at the time of data rewrite. The system board thus increases in area because of the IC socket mounted thereon, which also increases the system cost.
To solve such a problem, for example, Japanese Unexamined Patent Application Publication No. Hei 9-231065 has proposed a technique in which an external nonvolatile memory contains in advance a rewrite program for rewriting data of this external nonvolatile memory, and the rewrite program is copied to a volatile memory at the time of data rewrite. In this technique, executing the rewrite program on the volatile memory enables data rewrite without the detachment of the external nonvolatile memory from the system board.
Japanese Unexamined Patent Application Publication No. Hei 8-249016, for example, has also proposed a technique in which a microprocessor implements thereon a CPU core and an internal nonvolatile memory containing the foregoing rewrite program, and the CPU core's execution of the rewrite program on the internal nonvolatile memory realizes data rewrite without the detachment of the external nonvolatile memory from the system board.